Soils that contain large amounts of char are those that have experienced relatively frequent
natural fires over a period of millennia (Lehmann et al., 2008). Converting a fraction of
standing plant biomass to black carbon in soil constitutes net removal of CO2 from the
atmosphere (Forbes et al., 2006). A relatively minor under-estimation in our estimates for the
percentage converted could explain up to one-fifth of the so-called missing carbon sink, that
is the imbalance between carbon eliminated from forest and fossil fuels, against observed
atmospheric CO2 (Kuhlbusch, 1998).